Electro-Optic Polymer Waveguide Devices Incorporating Organically Modified Sol-Gel Clads

ABSTRACT

A method for making an optical device including establishing a temperature in a composition and applying an electric field to pole the core layer of the composition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation under 35 U.S.C. §120, which claimspriority to U.S. application Ser. No. 11/685,629, filed Mar. 13, 2007,which is a continuation of U.S. application Ser. No. 10/341,828, filedJan. 14, 2003, and issued on Apr. 17, 2007, as U.S. Pat. No. 7,206,490,which is a continuation-in-part under 35 U.S.C. §119 that claims thebenefit of U.S. application Ser. No. 10/299,155, filed Nov. 19, 2002,and issued on Aug. 30, 2005, as U.S. Pat. No. 6,937,811. The disclosuresof the prior applications are considered part of (and are incorporatedby reference in) the disclosure of this application.

BACKGROUND OF THE INVENTION

All patents, patent applications, and publications cited within thisapplication are incorporated herein by reference to the same extent asif each individual patent, patent application or publication wasspecifically and individually incorporated by reference.

This application is a continuation-in-part of patent application Ser.No. 10/299,155 filed Nov. 19, 2002, entitled “Polymer Waveguide DevicesIncorporating Electro-optically Active Polymer Clads,” which is assignedto the same assignee as the present application, and which is herebyincorporated by reference.

The invention relates generally to the field of electro-optic polymerwaveguide devices. The art of electro-optic polymer waveguide devicesand the use of organic second order nonlinear optical polymers in suchdevices is well documented. A typical electro-optic polymer waveguide,which is illustrated as a cross-sectional view in FIG. 1, is comprisedof: 1) an electro-optic polymer core (5); 2) a first polymer clad (10)overlying the electro-optic polymer core (5); 3) a second polymer clad(15) underlying the electro-optic polymer core (5); 4) a top electrode(20) overlying the first polymer clad (10); 5) a bottom electrode (25)underlying the second polymer clad (15); and 6) a substrate (30).

In a typical electro-optic polymer waveguide, the total thickness of thecore, first clad, and second clad is around 6-10 μm. Typically, therefractive indices of the polymer clads are chosen to confine a greatmajority of the optical field in the electro-optic polymer core and keepthe optical field from contacting the metal electrodes. The resultingmode in the waveguide is elliptical to such an extent that unacceptablyhigh insertion results when the waveguide is butt-coupled to an opticalfiber. The insertion loss can be reduced by using tapers to adjust thesize of the fiber mode to the size of the waveguide mode. However, suchtapers can be difficult to manufacture.

Making the waveguide mode less elliptical can also reduce insertionloss. A less elliptical waveguide mode can be achieved by decreasing thedifference in refractive indices between the clads and electro-opticcore. However, such an approach may lead to the optical field contactingone or both of the electrodes, which may cause increased optical loss orcomplete loss of mode confinement. Such a problem may be overcome byadding lower refractive index clads to act as barriers between the firstand second clads and metal electrodes.

Proper conductivity in the clads of an electro-optic device duringpoling is also advantageous. It is known in the art that insulatingproperties of some polymers detract from their use as passive clads inelectro-optic polymer modulators since some conductivity in clads isnecessary during poling of the electro-optic polymer. See, for example,Grote et al., Opt. Eng., 2001, 40(11), 2464-2473.

SUMMARY OF THE INVENTION

At the elevated temperatures required for poling, organically modifiedsol-gels (e.g., organically modified titania-siloxane sol-gels) havedesirable conductivity values (e.g., on the order of 10¹⁰ to 10¹¹ohm-cm⁻¹). Thus, an electro-optic waveguide device is described thatincludes an electro-optic polymer core having a refractive index and apolymer buffer clad that comprises an organically modified sol-gel. Therefractive index of the buffer clad is lower than the refractive indexof the core. The waveguide may further include: (a) an additionalpolymer buffer clad (e.g., comprising a crosslinked acrylate polymer)having a refractive index that is lower than the refractive index of theelectro-optic polymer core; (b) a first polymer clad (e.g., comprising acrosslinked acrylate polymer) between the electro-optic polymer core andthe additional polymer buffer clad, and having a refractive index thatis lower than the refractive index of the electro-optic polymer core buthigher than the refractive index of the polymer buffer clad thatcomprises the organically modified sol-gel; and (c) a second polymerclad between the electro-optic polymer core and the polymer buffer cladcomprising the organically modified sol-gel, the second polymer cladhaving a refractive index that is lower than the refractive index of theelectro-optic polymer core but higher than the refractive index of thepolymer buffer clad comprising the organically modified sol-gel. Eachlayer may be deposited directly on the preceding layer. Alternatively,individual pairs of layers may be separated by a thin (e.g., less thanabout 0.1 μm or so) adhesion promoter, surface promoter, primer layer,or the like.

As used herein, a “buffer clad” is the outermost layer from the core ofthe waveguide and has a refractive index sufficiently low to keep theoptical mode from contacting electrodes that would cause optical loss(e.g., gold electrodes).

The organically modified sol-gel clads increase the power efficiency ofthe device since the electro-optic polymer core can be more efficientlypoled. Additionally, the structure also decreases optical insertion losssince the propagating mode is both less elliptical due to the presenceof the buffer clads, and does not contact the metal electrodes due tothe buffer clads.

Other features and advantages will be apparent from the followingdescription of the preferred embodiments, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a typical prior art electro-optic polymer waveguidedevice.

FIG. 2 is a cross-sectional view of one embodiment of an electro-opticpolymer waveguide device.

FIG. 3 is a cross-sectional view of various electro-optic coreconfigurations in the polymer stack.

FIG. 4 is a cross-sectional view of another embodiment of anelectro-optic polymer waveguide device.

FIG. 5 is a graph of resistivity vs. temperature for an organicallymodified sol gel used as a buffer clad.

FIG. 6 is a cross-sectional view of various embodiments of anelectro-optic waveguide device.

DETAILED DESCRIPTION

In one embodiment, an electro-optic waveguide device comprises anelectro-optic polymer core and an electro-optic first polymer clad inproximity to the electro-optic polymer core, the electro-optic firstpolymer clad having a refractive index that is lower than the refractiveindex of the electro-optic polymer core. The electro-optic first polymerclad increases the power efficiency of the device since some of thepropagating mode resides in the first polymer clad. Both theelectro-optic core polymer layer and the electro-optic clad polymerlayer can be formed by methods known to those skilled in the art such asspin-coating, dip-coating, brushing, and printing.

In general, an electro-optic polymer comprises a second order nonlinearoptical chromophore and a polymer matrix. In some embodiments, thechromophore can be covalently attached to the polymer backbone. Theelectro-optic core can be poled by any one of the techniques known tothose skilled in the art including corona poling, electrode poling, orpush-pull poling. The electro-optic core can be shaped by reactive ionetching, laser ablation, bleaching, positive tone photolithography,negative tone photolithography, or embossing. Referring to FIG. 3, theelectro-optic core can be shaped as a “rib” (FIG. 3 a), a “quasi-rib”(FIG. 3 b), a “quasi-trench” (FIG. 3 c), or a “buried-trench” (FIG. 3d). Preferably, the electro-optic device is a Mach Zehnder modulator, adirectional coupler, or a micro-ring resonator.

In a preferred embodiment, the electro-optic waveguide device comprises,referring to FIG. 2: 1) an electro-optic polymer core (35); 2) anelectro-optic first polymer clad (40) in proximity to the electro-opticpolymer core, the electro-optic first polymer clad having a refractiveindex that is lower than the refractive index of the electro-opticpolymer core; 3) a second polymer clad (45) in proximity to theelectro-optic polymer core, the second polymer clad having a refractiveindex that is lower than the refractive index of the electro-opticpolymer core; 4) a first polymer buffer clad (50) in proximity to theelectro-optic first polymer clad, the first polymer buffer clad having arefractive index that is lower than the refractive index of theelectro-optic first polymer clad; and 5) a second polymer buffer clad(55) in proximity to the second polymer clad, the second polymer bufferclad having a refractive index that is lower than the refractive indexof the second polymer clad. The electro-optic polymer core,electro-optic first polymer clad, second polymer clad, first polymerbuffer clad, and second polymer buffer clad can each be formedindependently by methods known to those skilled in the art such asspin-coating, dip-coating, brushing, and printing. In anotherembodiment, the second polymer clad is an electro-optic polymer or,preferably, a crosslinked electro-optic polymer.

In another embodiment, the electro-optic waveguide device comprises,referring to FIG. 4: 1) an electro-optic polymer core (35); 2) anelectro-optic first polymer clad (40) in proximity to the electro-opticpolymer core, the electro-optic first polymer clad having a refractiveindex that is lower than the refractive index of the electro-opticpolymer core; 3) a first polymer buffer clad (50) in proximity to theelectro-optic first polymer clad, the first polymer buffer clad having arefractive index that is lower than the refractive index of theelectro-optic first polymer clad; and 4) a second polymer buffer clad(55) in proximity to the electro-optic polymer core, the second polymerbuffer clad having a refractive index that is lower than the refractiveindex of the electro-optic polymer core. The electro-optic polymer core,electro-optic polymer first clad, first polymer buffer clad, and secondpolymer buffer clad can each be formed independently by methods known tothose skilled in the art such as spin-coating, dip-coating, brushing,and printing.

The refractive index and thickness of each polymer layer is chosen sothat the resulting waveguide has single mode behavior. The refractiveindex of each layer, thickness of each clad, and the dimensions of thecore that would give single mode behavior in the resulting waveguide canbe calculated using techniques and computer programs known to thoseskilled in the art (such as the BeamProp Version 5.0 software fromRsoft). Preferable ranges for the thickness and the refractive index ofthe various layers are summarized in Table 1. Preferably, referring toFIG. 2, the electro-optic core (35) is shaped as a rib and has athickness of about 2.4-about 3.8 μm and a refractive index of about1.54-about 1.62, the electro-optic first polymer clad (40) has athickness between the electro-optic core surface (60) and theelectro-optic first polymer clad surface (65) of about 1.0-about 3.0 μmand a refractive index of about 1.53-about 1.61, the second polymer clad(45) has a thickness of O— about 3.0 μm and a refractive index of about1.53-about 1.61, the first polymer buffer clad (50) has a thickness ofabout 2.2-about 3.2 μm and a refractive index of about 1.445-about1.505, and the second polymer buffer clad has a thickness of about2.2-about 3.2 μm and a refractive index of about 1.445-about 1.505. Thepreferable ranges for refractive index, layer thickness, and coredimensions for the various layers are given below in Table 1. TABLE 1Thickness Width Layer (μm) (μm) Refractive Index First Polymer BufferClad 2.2-3.2 — 1.445-1.505 First Polymer Clad 1.0-3.0 — 1.53-1.61 Core2.4-3.8 2.8-4.2 1.54-1.62 Second Polymer Clad  0-3.0 — 1.53-1.61 SecondPolymer Buffer Clad 2.2-3.2 — 1.445-1.505

In another embodiment, the electro-optic core is crosslinked, theelectro-optic first polymer clad is crosslinked, the second polymer cladis an organically modified sol-gel (ORMOSIL), the first polymer bufferclad is a radiation-cured acrylate, and the second polymer buffer cladis an organically modified sol-gel. Crosslinkable electro-opticpolymers, sol-gels, ORMOSILs, and radiation cured acrylates are known tothose skilled in the art, for example see U.S. Pat. Nos. 6,419,989;6,335,149; 6,323,361; 6,306,563; 6,303,730; 6,294,573; 6,126,867;6,002,828; 5,811,507; 5,783,319; 5,776,374; 5,635,576; 5,714,304;5,480,687; 5,433,895; 5,223,356; and 5,120,339; Chem. Mater. 2000, 12,1187; J. Am. Chem. Soc. 2001, 123, 986; Macromolecules 1992, 25, 4032;and Chem. Mater. 1998, 10, 146. Preferably, the second polymer cladcomprises an organically modified titania-siloxane sol-gel.

The ORMOSILs are particularly useful as buffer clads, with or withoutadditional polymer clads, because at the elevated temperatures requiredfor poling, they have desirable conductivity values (10¹⁰ to 10¹¹ohm-cm⁻¹), with the transition occurring around 100° C., as shown inFIG. 5. In addition, these materials enable refractive index tunabilitybased on their flexibility of composition. For example, replacingaliphatic groups such as methyl groups with more polarizable groups suchas phenyl groups on the silicon atoms of an ORMOSIL or an organicallymodified titania-siloxane sol-gel will increase the refractive index.Increasing the fraction of titania will also increase the refractiveindex. Thus, one embodiment is an electro-optic waveguide devicecomprising an electro-optic polymer core and a polymer buffer clad,wherein the polymer buffer clad comprises an organically modified solgel and has a refractive index that is lower than the refractive indexof the electro-optic polymer core.

Preferably, as shown in FIG. 6, the electro-optic waveguide devicecomprises a first polymer buffer clad (75), an electro-optic core (70),and a second polymer buffer clad (80) wherein one polymer buffer cladcomprises an organically modified sol-gel, and each of the buffer cladshas a refractive index that is lower than the refractive index of theelectro-optic polymer core. Suitable materials for the other polymerbuffer clad include crosslinked acrylate polymers, e.g., of the typedescribed in Oh et al., Appl. Phys. Lett. 2000, 76(24), 3525-3527. Thedevice may also further include a first polymer clad (85) between thecore (70) and first buffer clad (75). The first polymer clad (85) has arefractive index that is lower than the refractive index of the core(70), but higher than the refractive index of first buffer clad (75).Preferably, the first polymer clad comprises a crosslinked acrylatepolymer.

In a another embodiment, the first polymer buffer clad has a thicknessof about 2.2 to about 3.2 μm and a refractive index of about 1.445 toabout 1.505, the first polymer clad has a thickness of about 1.0 toabout 3.0 μm and a refractive index of about 1.53 to about 1.61, theelectro-optic polymer core has a thickness of about 2.4 to about 3.8 μmand a refractive index of about 1.54 to about 1.62, and the secondpolymer buffer clad has a thickness of about 2.2 to about 3.2 μm and arefractive index of about 1.445 to about 1.505.

In another embodiment, the electro-optic waveguide device furthercomprises a second polymer clad between the electro-optic polymer coreand the second polymer clad, the second polymer clad having a refractiveindex that is lower than the refractive index of the electro-opticpolymer core and higher than the refractive index of the second polymerbuffer clad. Preferably, the second polymer clad comprises anorganically modified sol-gel, more preferably an organically modifiedtitania-siloxane sol-gel. Preferably, the first polymer buffer clad hasa thickness of about 2.2 to about 3.2 μm and a refractive index of about1.445 to about 1.505; (b) the first polymer clad has a thickness ofabout 1.0 to about 3 μm and refractive index of about 1.53 to about1.61; (c) the electro-optic polymer core has a thickness of about 2.4 toabout 3.8 μm and a refractive index of about 1.54 to about 1.62; (d) thesecond polymer clad has a thickness of about 1.0 to about 3.0 μm and arefractive index of about 1.53 to about 1.61; and (e) the second polymerbuffer clad has a thickness of about 2.2 to about 3.2 μm and arefractive index of about 1.445 to about 1.505.

Preferably, in all embodiments, the electro-optic polymer core (70)comprises a crosslinked polymer (e.g., a crosslinked acrylate polymer).Preferably, the electro-optic waveguide device further comprises asubstrate on which the polymer buffer clad comprising an organicallymodified sol-gel is deposited. In some embodiments, the substrate issilicon.

The optical waveguide devices described herein can be used in opticalcommunications systems. The optical communications systems employingsuch modulators will be improved due to the increased power efficiencyof the waveguide devices. Thus, other embodiments of the inventioninclude communications systems such as beam steering systems, phasedarray radars, optical routers, optical transponders, and opticalsatellites.

EXAMPLES

The following example(s) is illustrative and does not limit the claims.

The preparation of materials used in the following examples is givenbelow:

Electro-Optic Polymers:

The electro-optic chromophore used in the electro-optic core andelectro-optic clad was prepared by esterifying a chromophore containingfree alcohol groups with the required equivalents of4-(trifluorovinyloxy)-benzoyl chloride (the benzoyl chloride isdescribed in U.S. Pat. No. 5,198,513) and a hindered amine base orpyridine.

The polymer used as a matrix for the electro-optic chromophore wasprepared by reacting 1-lithio-4-trifluovinyloxybenzene withpentafluorostyrene at −78° C. for 1 h followed by warming to roomtemperature. The resulting 2,3,5,6-fluoro-4′-trifluorovinyloxy-4-vinylbiphenyl was purified by column chromatography and polymerized with AIBNinitiation in THF under N₂ atmosphere. The polymer was purified byprecipitation from THF/hexanes.

Polymers for the Second Buffer Clad and/or Second Polymer Clad:

Polymer (1): an organically modified titania-siloxane sol-gel wasprepared by: 1) dripping 127.2 g of titanium butoxide (from Aldrich,double distilled) into a solution of 592 g of anhydrous ethanol and 24.0g of concentrated DCl (37 wt %); 2) dripping 94.3 g of D₂O; 3) dripping99.2 g of glycidoxypropyltrimethoxysilane; 4) heating at ˜80° C. for 12hours; 5) dripping 372.0 g of phenyltriethoxysilane (from Aldrich,distilled) while at ˜80° C. for 4 hours; and 6) adding distilled 473 gof cyclohexanone into the solution and stir to homogeneity. The lowboiling volatiles from the reaction were removed by rotary evaporation.Finally, 1.60 g ofpoly[dimethylsiloxane-co-methyl(3-hydroxypropyl)siloxane]-graft-poly(ethylene/-propyleneglycol) (from Aldrich, used as received) was added into the abovesolution and stirred to obtain a homogeneous solution.

Polymer (2): an organically modified sol-gel was prepared by: 1) adding156.0 g tetraethyl orthosilicate (from Aldrich, double distilled), 531.0g glycidoxypropyl-trimethoxysilane (from Aldrich, double distilled),321.0 g cyclohexanone (from Aldrich, distilled) to a flask; 2) drippinga solution of 187.5 g D₂O and 7.50 g 2M DCl; and 3) heating at 80-100°C. for 5 hours.

Polymer (3): an organically modified sol-gel was prepared by 1) adding17.83 g methyltriethoxysilane (from Aldrich, double distilled), 70.80 gglycidoxypropyl-trimethoxysilane (from Aldrich, double distilled), 64.2g cyclohexanone (from Aldrich, distilled) to a flask; 2) dripping asolution of 21.78 g D₂O and 2.050 g 2M DCl; and 3) heating at 80-100° C.for 5 hours.

Polymers for the First Polymer Clad and First Polymer Buffer Clad:

Polymer (4): a crosslinkable acrylate polymer was prepared by: 1)stirring 20.0 g of pentaerythritol tetraacrylate (Aldrich, used asreceived) and 20.0 g tri(ethylene glycol) dimethacrylate (Aldrich, usedas received); 2) adding 1.2 g of2-methyl-4′-(methylthio)-2-morpholinopropiophenone and stirring untildissolution; and 3) refrigerating the resulting solution.

Polymer (5): another crosslinkable acrylate polymer was prepared by: 1)adding to a two-liter flask with mechanical stirring 400.0 g Bisphenol Aglycerolate diacrylate (Aldrich, used as received), 70.4 g tri(ethyleneglycol) dimethacrylate (Aldrich, used as received), and 552 g2-ethoxyethanol (Aldrich, distilled), and stirring either overnight orfor 12 hours to obtain a homogeneous solution; and 2) introducing 4.704g 2-methyl-4′-(methylthio)-2-morpholinopropiophenone into the solution,and stirring to effect complete dissolution.

Example 1

The device in this example was fabricated using a gold covered SiO₂6-inch wafer as a substrate. The refractive indices reported aremeasured at 1550 nm.

An adhesion promoter for the second polymer buffer clad and gold wasprepared by: 1) heating 100.0 g of isopropyl alcohol (from Aldrich), 2.0g of H₂O, 5.0 g of mercapto-propyltriethoxysilane (from Sigma,distilled) and 5.0 g of mercaptopropylmethyl-dimethoxysilane, and twodrops of 37% HCl at reflux for 2 hours; 2) allowing the solution cooldown to room temperature; 3) adding 504 g of isopropyl alcohol to theabove solution and stirring. The adhesion promoter was applied to thegold surface by spin depositing a 1% solution at 500 rpm for 2 secondsand 4500 rpm for 30 seconds.

The second polymer buffer clad (Polymer (2)) was spin deposited as a36.1% (by weight) solution in cyclopentanone at 300 rpm for 12 secondsand 1050 rpm for 20 seconds. The wafer layer was cured by heating under50 Torr of vacuum at 100° C. for 60 min (heating rate of 0.5° C./min),150° C. for 60 min (heating rate of 3° C./min), and 200° C. for 30 min(heating rate of 5° C./min), and cooling the wafer to ambienttemperature at a cooling rate of 0.5° C./min. The thickness of the layeris 2.9 μm and the refractive index is 1.475.

The second polymer clad (Polymer (1)) was spin deposited on the secondpolymer buffer clad as a 38% (by weight) solution in cyclohexanone at500 rpm for 5 seconds and 2900 rpm for 30 seconds. The clad was cured byheating under 50 Torr of vacuum at 100° C. for 60 min (heating rate of0.5° C./min), 150° C. for 60 min (heating rate of 3° C./min), and 190°C. for 90 min (heating rate of 5° C./min), and cooling the wafer toambient temperature at a cooling rate of 0.5° C./min. The thickness ofthe layer was 1.9 μm and the refractive index was 1.545.

An adhesion promoter layer was applied to the second polymer clad byspin depositing a 1% (by weight) solution of(N-(2-aminoethyl)-3-aminopropylmethyl-dimethoxysilane) in isopropylalcohol at 500 rpm for 5 sec and 3000 rpm for 30 sec. The wafer was thenheated on a hot plate at 100° C. for 5 min.

The polymer used for the electro-optic core was spin deposited on thesecond polymer clad as a 30% (by total solids weight) solution of theelectro-optic chromophore in the polymer matrix (the chromophoreconcentration with respect to the crosslinkable polymer was 25% byweight) in cyclopentanone at 300 rpm for 2 sec then 500 rpm for 5 sec,then 1000 rpm for 20 sec. The film was precured by heating at 80° C. ona hot plate for 10 min, heating at 70° C. at 1 mTorr for 480 min. Thefilm was corona poled and crosslinked by applying a voltage of 4.5 kV tothe wafer while heating to 180° C. over 10 min, holding at 4.5 kV at180° C. for 10 min, increasing the corona voltage to 7.5 kV and holdingat 180° C. for 10 min, and cooling to ambient temperature over 25 min.Heating at 180° C. was necessary to affect the desired amount ofcrosslinking. The thickness of the layer was 3.0 μm and the refractiveindex was 1.565.

The electro-optic polymer core was formed as a rib using a hardmask anddry etching as described in commonly assigned, co-pending U.S.application Ser. No. 10/264,461. The electro-optic polymer core wasformed as a Mach-Zehnder Modulator.

The polymer used for the electro-optic first polymer clad was spindeposited on the electro-optic core and the second polymer clad as a 23%(by total solids weight) solution of the electro-optic chromophore inthe polymer matrix (the chromophore concentration with respect to thecrosslinkable polymer was 21% by weight) in cyclopentanone at 300 rpmfor 2 sec then 500 rpm for 5 sec, then 1400 rpm for 20 sec. The film wasprecured by heating at 50° C. on a hot plate for 10 min., followed byheating at 25 Torr for 8 h at 50° C. The film was corona poled andcrosslinked by applying a voltage of 7.5 kV to the wafer while heatingat 180° C. for 20 min. The thickness of the layer was 1.2 μm and therefractive index was 1.55.

The first polymer buffer clad (Polymer (4)) was spin deposited on theelectro-optic first polymer clad as a liquid at 500 rpm for 5 secondsand 1800 rpm for 40 seconds. The wafer was then exposed to UV radiationuntil the film was hardened. The thickness of the layer was 3.1 μm andthe refractive index was 1.495.

The surface of the first polymer buffer clad was treated withoxygen/neon plasma for 7 min. in order to promote adhesion of a goldlayer. The gold layer was deposited and the gold electrode was definedover one arm of the Mach-Zehnder modulator by photolithography and wetetching. The wafer was diced into individual Mach-Zehnder electro-opticdevices.

Example 2

The device in this example was fabricated using a gold-covered SiO₂,6-inch wafer as a substrate. The second polymer buffer clad, secondpolymer clad, and the electro-optic polymer core were the same as thoseused in Example 1. The refractive indices reported are measured at 1550nm.

The electro-optic polymer core was formed as a rib using a hardmask anddry etching as described in commonly assigned, co-pending U.S.application Ser. No. 10/264,461. The electro-optic polymer core wasformed as a Mach-Zehnder modulator.

The surface of the stack was treated with oxygen plasma for 1 min. in aDRIE at a working pressure of 230 mTorr to promote adhesion of thesubsequently deposited first polymer buffer clad.

A 24% by weight solution of the first polymer clad (Polymer (5)) wasspin deposited at 300 rpm for 30 sec and 1000 rpm for 20 sec. The filmwas dried at 50° C. at 1 mTorr for 1 hour, and then exposed toultraviolet radiation until the film was hardened. The thickness of thelayer was 2 μm and the refractive index was 1.543.

The surface of the first polymer clad was treated with an oxygen/neonplasma in a DRIE at a working pressure of 20 mTorr for 5 min. to promoteadhesion of the first polymer buffer clad. The first polymer buffer cladand top electrode were the same as those provided in Example 1, and weredeposited using the procedure described in Example 1.

Other embodiments are within the following claims.

1. A method for making an optical device comprising: establishing atemperature in a composition including at least one buffer cladding andan electro-optic polymer core layer sufficient to reduce electricalresistivity of at least a portion of the buffer cladding; and applyingan electric field through the buffer cladding to pole the electro-opticpolymer core layer.
 2. The method of claim 1, wherein the temperature issufficient to enable a polymerization reaction in the electro-opticcore.
 3. The method of claim 2, wherein the polymerization reactionincludes a cross-linking reaction.
 4. The method of claim 1, wherein thetemperature is about 180° C.
 5. The method of claim 1, wherein thebuffer cladding includes an organically-modified sol-gel.
 6. The methodof claim 1, wherein the buffer cladding is reduced to an electricalresistivity of 10¹¹ ohm·cm⁻¹ or less.
 7. The method of claim 1, whereinafter poling, the refractive index of the buffer cladding is lower thanthe refractive index of the core.
 8. The method of claim 1, wherein theelectro-optic core layer is poled while the composition is at atemperature sufficient for a crosslinking polymerization reaction of thecore layer and sufficient for a reduction in electrical resistivity ofthe buffer cladding.
 9. The method of claim 1, wherein the electricfiled is applied through the buffer cladding and through a polymercladding between the buffer cladding and core layer to pole theelectro-optic polymer core layer.
 10. The method of claim 1, wherein theelectrical field is applied using a corona, an electrode, or a push-pullapparatus.
 11. A method for making an optical device, comprising:heating a composition including a buffer cladding including anorganically modified sol-gel, a polymer cladding, and an electro-opticpolymer core; and applying an electric field through the buffer claddingand polymer cladding to pole the electro-optic polymer core.
 12. Themethod of claim 11, wherein the composition is heated to a temperaturesufficient to crosslink the electro-optic polymer core.
 13. The methodof claim 11, wherein the composition is heated to a temperaturesufficient to lower the resistivity of the buffer cladding.
 14. Themethod of claim 11, further comprising applying a second polymercladding and second buffer cladding.
 15. The method of claim 14, furthercomprising applying a metal layer on the second buffer cladding.
 16. Themethod of claim 11, further comprising applying a second buffercladding.
 17. The method of claim 11, wherein the electro-optic coreincludes an organically-modified sol-gel.
 18. The method of claim 11,further comprising shaping the electro-optic polymer core.
 19. Themethod of claim 14, wherein the second polymer cladding includes anorganically-modified sol-gel.
 20. A composition for use in making anoptical device, comprising: a conductive layer; and a buffer claddingincluding an organically modified sol-gel.
 21. The composition of claim20, further comprising a polymer cladding including an organicallymodified sol-gel adjacent to the buffer cladding.
 22. The composition ofclaim 21, wherein the polymer cladding includes an organically modifiedtitania-siloxane sol-gel.
 23. The composition of claim 20, furthercomprising an adhesion promoter between the conductive layer and thebuffer cladding.
 24. The composition of claim 20, wherein the conductivelayer includes a metallic layer.
 25. The composition of claim 20,further comprising a semiconductor; and wherein the conductive layer isdisposed on the semiconductor; and the buffer cladding is disposed onthe conductive layer.